Moving picture prediction system

ABSTRACT

To achieve an encoding system including a highly efficient prediction performed in response to the content of a scene, a significance, and a motion characteristic of a moving picture and the like, memories a, b, c, motion compensator  5  responsive to an arbitrary transform parameter representing the motion of a prediction picture segment for generating a predicted picture by using arbitrary data stored in the memories a, b, c based upon the transform parameter, and memory update unit  15  for allowing the content of one or more of the memories to be updated at an arbitrary period of time, are provided.

CROSS REFERENCE PARAGRAPH

This application is a Divisional of co-pending application Ser. No.10/642,508, filed on Aug. 18, 2003, the entire contents of which arehereby incorporated by reference and for which priority is claimed under35 U.S.C. §120.

TECHNICAL FIELD

The present invention relates to the prediction of a moving pictureimplemented, for example, in

a moving picture encoder/decoder used in a portable/stationary videocommunication device and the like for visual communications in a videotelephone system, a video conference system or the like,

a moving picture encoder/decoder used in a picture storage/recordingapparatus such as a digital VTR and a video server, and

a moving picture encoding/decoding program implemented in the form of asingle software or a firmware as a Digital Signal Processor (DSP).

BACKGROUND ART

MPEG-4 (Moving Picture Experts Group Phase-4) Video Encoding/DecodingVerification Model (hereinafter referred to by the initials VM) whosestandardization is in progress by ISO/IEC JTC1/SC29/WG11 may beintroduced as a conventional type of predictive encoding/decoding in anencoding/decoding system of moving pictures. The VM continues to reviseits contents according to the progress being made in standardization ofMPEG-4. Here, Version 5.0 of the VM is designated to represent the VMand will be simply referred to as VM hereinafter.

The VM is a system for encoding/decoding each video object as one unitin view of a moving picture sequence being an aggregate of video objectschanging their shapes time-/space-wise arbitrarily. FIG. 29 shows a VMvideo data structure. According to the VM, a time-based moving pictureobject is called a Video Object (VO), and picture data representing eachtime instance of the VO, as an encoding unit, is called a Video ObjectPlane (VOP). If the VO is layered in time/space, a special unit called aVideo Object Layer (VOL) is provided between the VO and the VOP forrepresenting a layered VO structure. Each VOP includes shape informationand texture information to be separated. If the moving picture sequenceincludes a single VO, then the VOP is equated to a frame. There is noshape information included, in this case, and the texture informationalone is then to be encoded/decoded.

The VOP includes alpha data representing the shape information andtexture data representing the texture information, as illustrated inFIG. 30. Each data are defined as an aggregate of blocks(alphablocks/macroblocks), and each block in the aggregate is composedof 16×16 samples. Each alphablock sample is represented in eight bits. Amacroblock includes accompanied chrominance signals being associatedwith 16×16 sample luminance signals. VOP data are obtained from a movingpicture sequence externally processed outside of an encoder.

FIG. 31 is a diagram showing the configuration of a VOP encoderaccording to the VM encoding system. The diagram includes original VOPdata P1 to be inputted, an alphablock P2 representing the shapeinformation of the VOP, a switch P3 a for passing the shape information,if there is any, of the inputted original VOP data, a shape encoder P4for compressing and encoding the alphablock, compressed alphablock dataP5, a locally decoded alphablock P6, texture data (a macroblock) P7, amotion detector P8, a motion parameter P9, a motion compensator P10, apredicted picture candidate P11, a prediction mode selector P12, aprediction mode P13, a predicted picture P14, a prediction error signalP15, a texture encoder P16, texture encoding information P17, a locallydecoded prediction error signal P18, a locally decoded macroblock P19, asprite memory update unit P20, a VOP memory P21, a sprite memory P22, avariable-length encoder/multiplexer P23, a buffer P24, and an encodedbitstream P25.

FIG. 32 shows a flowchart outlining an operation of the encoder.

Referring to the encoder of FIG. 31, the original VOP data P1 aredecomposed into the alphablocks P2 and the macroblocks P7 (Steps PS2 andPS3). The alphablocks P2 and the macroblocks P7 are transferred to theshape encoder P4 and the motion detector P8, respectively. The shapeencoder P4 is a processing block for data compression of the alphablockP2 (step PS4), the process of which is not discussed here further indetail because the compression method of shape information is notparticularly relevant to the present invention.

The shape encoder P4 outputs the compressed alphablock data P5 which istransferred to the variable-length encoder/multiplexer P23, and thelocally decoded alpha data P6 which is transferred sequentially to themotion detector P8, the motion compensator P10, the prediction modeselector P12, and the texture encoder P16.

The motion detector P8, upon reception of the macroblock P7, detects alocal-motion vector on a macroblock basis using reference picture datastored in the VOP memory P21 and the locally decoded alphablock P6 (stepPS5). Here, the motion vector is one example of a motion parameter. TheVOP memory P21 stores the locally decoded picture of a previouslyencoded VOP. The content of the VOP memory P21 is sequentially updatedwith the locally decoded picture of a macroblock whenever the macroblockis encoded. In addition, the motion detector P8 detects a global warpingparameter, upon reception of the full texture data of the original VOP,by using reference picture data stored in the sprite memory P22 andlocally decoded alpha data. The sprite memory P22 will be discussedlater in detail.

The motion compensator P10 generates the predicted picture candidate P11by using the motion parameter P9, which is detected in the motiondetector P8, and the locally decoded alphablock P6 (step PS6). Then, theprediction mode selector P12 determines the final of the predictedpicture P14 and corresponding prediction mode P13 of the macroblock byusing a prediction error signal power and an original signal power (stepPS7). In addition, the prediction mode selector P12 judges the codingtype of the data either intra-frame coding or inter-frame coding.

The texture encoder P16 processes the prediction error signal P15 or theoriginal macroblock through Discrete Cosine Transformation (DCT) andquantization to obtain a quantized DCT coefficient based upon theprediction mode P13. An obtained quantized DCT coefficient istransferred, directly or after prediction, to the variable-lengthencoder/multiplexer P23 to be encoded (steps PS8 and PS9). Thevariable-length encoder/multiplexer P23 converts the received data intoa bitstream and multiplexes the data based upon predetermined syntaxesand variable-length codes (step PS10). The quantized DCT coefficient issubject to dequantization and inverse DCT to obtain the locally decodedprediction error signal P18, which is added to the predicted pictureP14, and the locally decoded macroblock P19 (step PS11) is obtained. Thelocally decoded macroblock P19 is written into the VOP memory P21 andthe sprite memory P22 to be used for a later VOP prediction (step PS12).

Dominant portions of prediction including a prediction method, a motioncompensation, and the update control of the sprite memory P22 and theVOP memory P21 will be discussed below in detail.

(1) Prediction Method in the VM

Normally, four different types of VOP encoding shown in FIG. 33 areprocessed in the VM. Each encoding type is associated with a predictiontype or method marked by a circle on a macroblock basis. With an I-VOP,intra-frame coding is used singly involving no prediction. With a P-VOP,past VOP data can be used for prediction. With a B-VOP, both past andfuture VOP data can be used for prediction.

All the aforementioned prediction types are motion vector based. On theother hand, with a Sprite-VOP, a sprite memory can be used forprediction. The sprite is a picture space generated through astep-by-step mixing process of VOPs based upon a warping parameter set{right arrow over (α)}=(a, b, c, d, e, f, g, h)detected on a VOP basis (The mark → denotes a vector hereinafter). Thewarping parameter set is determined by the following parametricequations.x′=(ax+by+c)/(gx+hy+1)y′=(dx+ey+f)/(gx+hy+1)The sprite is stored in the sprite memory P22.

Referring to the parametric equations, (x, y) represents the pixelposition of an original VOP in a two-dimensional coordinate system. (x′,y′) represents a pixel position in the sprite memory corresponding to(x, y,) based upon a warping parameter. With the Sprite-VOP, the warpingparameter set can be used uniformly with each macroblock to determine(x′, y′) in the sprite memory for prediction to generate a predictedpicture. In a strict sense, the sprite includes “Dynamic Sprite” usedfor prediction and “Statistic Sprite” used for prediction as well as foranother purpose of an approximate representation of VOP at a decodingstation. In FIGS. 34 through 37 below, “sprite” stands for DynamicSprite.

The motion detector P8 detects the motion vector and the warpingparameter to be used for the aforementioned prediction types. The motionvectors and the warping parameters are generically called the motionparameter P9 hereinafter.

(2) Motion Compensation

FIG. 34 is a diagram showing the configuration of the motion compensatorP10 in detail. In the figure, a warping parameter P26, a motion vectorP27, a global-motion compensator P28, a local-motion compensator P29, awarping-parameter based predicted picture candidate P30, and amotion-vector based predicted picture candidate P31 are shown. Thewarping-parameter and motion-vector based predicted picture candidates30, 31 are generically called the predicted picture candidates P11hereinafter.

FIG. 35 shows a flowchart outlining the operation of the motioncompensator P10 including steps PS14 through PS21.

The motion compensator P10 generates the predicted picture candidate P11using the warping parameter P26 of a full VOP detected on a macroblockP7 basis in the motion detector P8 or a macroblock based motion vectorP27. The global-motion compensator P28 performs a motion compensationusing the warping parameter P26, and the local-motion compensator P29performs a motion compensation using the motion vector P27.

With the I-VOP, the motion compensator P10 does not operate. (Theoperating step proceeds to step PS21 from step PS14.) With a VOP otherthan the I-VOP, the local-motion compensator P29 reads out a predictedpicture candidate PR1 from the locally decoded picture of a past VOPstored in the VOP memory P21 by using the motion vector P27 (step PS15).With the P-VOP, the predicted picture candidate PR1 is only available tobe used.

When the B-VOP is identified in step PS16, the local-motion compensatorP29 further reads out a predicted picture candidate PR2 from the locallydecoded picture of a future VOP stored in the VOP memory P21 by usingthe motion vector P27 (step PS17). In addition, an arithmetic mean ofthe predicted picture candidates PR1, PR2 obtained from the past andfuture VOP locally decoded pictures to obtain a predicted picturecandidate PR3 (step PS18).

A predicted picture candidate PR4 is generated also through DirectPrediction (step PS19). (Direct Prediction is based upon a predictionmethod corresponding to B-Frame in an encoding method H.263,Recommendation ITU-T. A vector for B-Frame is produced based upon agroup of P-VOP vectors, which is not discussed further here in detail.)In FIG. 34, the motion-vector based predicted picture candidates P31 isa generic term for all or part of the predicted picture candidates PR1through PR4.

If a VOP is of neither I-VOP nor B-VOP, then the VOP is of Sprite-VOP.With the Sprite-VOP, the predicted picture candidate PR1 is read outfrom the VOP memory based upon the motion vector. In addition, theglobal-motion compensator P28 reads out the predicted picture candidateP30 from the sprite memory P22 based upon the warping parameter P26 instep PS20.

The global-motion compensator P28 calculates the address of a predictedpicture candidate in the sprite memory P22 based upon the warpingparameter P26, and reads out the predicted picture candidate P30 fromthe sprite memory P22 to be outputted based upon a resultant address.The local-motion compensator P29 calculates the address of a predictedpicture candidate in the VOP memory P21 based upon the motion vector P27and reads out the predicted picture candidate P31 to be outputted basedupon a resultant address.

These predicted picture candidates P11 are evaluated along with anintra-frame coding signal of the texture data P7 in the prediction modeselector P12, which selects a predicted picture candidate having theleast power of a prediction error signal along with a prediction mode.

(3) Updating of Memories

The memory update unit P20 controls the VOP memory P21 and sprite memoryP22 to be updated (step PS12). The contents of these memories areupdated regardless of the prediction mode P13 selected on a macroblockbasis.

FIG. 36 is a diagram showing the configuration of the memory update unitP20. FIG. 37 shows a flowchart including steps PS22 through PS28illustrating the operation of the memory update unit P20.

In FIG. 36, an externally supplied VOP encoding type P32, an externallysupplied sprite prediction identification flag P33 for indicating theuse of the sprite memory for prediction, an externally supplied blendfactor P34 used for prediction with the sprite memory, switches P35,P36, a sprite blender P37, a sprite transformer P38, a VOP memory updatesignal P39, and a sprite update signal P40 are shown.

Firstly, the use of the sprite with the current VO or VOL is examined ifbeing designated by the sprite prediction identification flag P33 (stepPS22). With no use of the sprite designated, the data are examined ifbeing the B-VOP (step PS27). With the B-VOP, then no updating isperformed with the VOP memory P21. With either the I-VOP or the P-VOP,then the VOP memory P21 is written over with the locally decodedmacroblock P19 on a macroblock basis (step PS28).

With the use of the sprite designated in step PS22, then the VOP memoryP21 is updated in the same manner as above (steps PS23, PS24), and inaddition, the sprite memory PS22 is updated through the followingprocedure.

a) Sprite Warping (Step PS25)

In the sprite transformer P38, an areaM({right arrow over (R,)}t−1)in the sprite memory P22 (M({right arrow over (R,)}t−1) is an areahaving the same size as that of a VOP having the origin of thecoordinates at a position in the sprite memory P22 with the VOP at atime t) is subject to warping (transformation) based upon a warpingparameter{right arrow over (α)}=(a,b,c,d,e,f,g,h).b) Sprite Blending (Step PS26)

By using a resultant warped picture from a) above, a new sprite memoryarea is calculated in the sprite blender P37 according to the followingexpression,M({right arrow over (R)},t)=(1−α)·W _(b) [M(R{right arrow over(,t)}−1),α]{right arrow over (+α)}·VO(r,{right arrow over (t),)}where α is the blend factor P34, W_(b)[M,{right arrow over (α])} is theresultant warped picture, and VO({right arrow over (r,)}t) is a pixelvalue of a locally decoded VOP with a location {right arrow over (r)}and a time t.

With a non-VOP area in a locally decoded macroblock, it is assumed thatVO({right arrow over (r,)}t)=0.As the blend factor α is assigned on a VOP basis, a locally decoded VOPis collectively blended into the sprite memory P22 based upon a weightα, regardless of the contents of a VOP area.

According to the aforementioned prediction system in the conventionalencoding system, the video object is predicted by using the memorydesigned to be used for detecting the motion vector alone and the memorydesigned to be used for detecting the warping parameter alone, both ofwhich are structurally allowed the maximum use of a single screen aloneeach. Thus, the limited use of reference pictures is only available forprediction, thereby hindering a sufficient improvement in predictionefficiency.

Further, in such a system where two or more video objects are encodedconcurrently, these memories only include a reference picturerepresenting the past record of a video object to be predicted alone,which limits the variation of a reference picture and precludes theutilization of a correlation among video objects for prediction.

Further, the memories are updated regardless of such items as theinternal structure, a characteristic, and the past record of the videoobject. This results in the insufficient storage of information lackingsignificant data for predicting a video object, thereby posing a problemof failing to enhance prediction efficiency.

The present invention is directed to solving the aforementionedproblems. An objective of this invention is to provide the predictionsystem for encoding/decoding of picture data where two or more memoriesare provided to store the past record of the moving picture sequenceeffectively in consideration of the internal structure andcharacteristic of the moving picture sequence, thereby achieving ahighly efficient prediction as well as encoding/decoding. In addition,the prediction system provides a sophisticated inter-video objectprediction performing among two or more video objects.

DISCLOSURE OF THE INVENTION

According to the present invention, a moving picture prediction system,for predicting a moving picture to be implemented in at least one of anencoder and a decoder, includes a plurality of memories for storingpicture data for reference to be used for prediction, the plurality ofmemories being corresponding to different transform methods,respectively, and a prediction picture generation section for receivinga parameter representing a motion of a picture segment to be predicted,and for generating a predicted picture using the picture data stored inone of the plurality of memories used for the picture segment to bepredicted based upon the parameter and one of the transform methodscorresponding to the one of the plurality of memories.

The encoder generates a prediction memory indication information signalindicating the one of the plurality of memories used for generating thepredicted picture and transmits the prediction memory indicationinformation signal and the parameter to a decoding station so as togenerate the predicted picture using the picture data stored in the oneof the plurality of memories based upon the one of the transform methodscorresponding to the one of the plurality of memories in the decodingstation.

The decoder receives the parameter and a prediction memory indicationinformation sinai indicating the one of the plurality of memories usedfor generating the predicted picture from an encoding station, whereinthe prediction picture generation section generates the predictedpicture using the picture data stored in the one of the plurality ofmemories based upon the parameter and the one of the transform methodscorresponding to the one of the plurality of memories.

Further, according to the present invention, a moving picture predictionsystem, for predicting a moving picture to be implemented in at leastone of an encoding and a decoding, includes a plurality of memories forstoring picture data for reference to be used for prediction, theplurality of memories being assigned to different parameter effectivevalue ranges, respectively, and a prediction picture generation sectionfor receiving a parameter representing a motion of a picture segment tobe predicted, for selecting one of the plurality of memories assigned toone of the parameter effective value ranges including a value of theparameter, and for generating a predicted picture using the picture datastored in a selected memory.

Still further, according to the present invention, a moving pictureprediction system, for predicting a moving picture to be implemented inat least one of an encoding and a decoding, includes a plurality ofmemories for storing picture data for reference to be used forprediction and a prediction picture generation section including amotion compensator for receiving a parameter representing a motion of apicture segment to be predicted, and for generating a predicted pictureby using the picture data stored in the plurality of memories based uponthe parameter, and a memory update unit for updating the picture datastored in at least one of the plurality of memories at an arbitrarytiming.

The moving picture prediction system predicts the moving picture in amoving picture sequence having first and second video objects, whereinthe plurality of memories includes separate first and second pluralitiesof memories corresponding to the first and second video objects,respectively, and the prediction picture generation section includesseparate first and second generators, respectively, corresponding to thefirst and second video objects, wherein the first generator uses thepicture data stored in at least one of the first and second pluralitiesof memories to generate the predicted picture when predicting the firstobject, and generates information indicating a use of the secondplurality of memories for predicting the first object, the informationbeing added to the predicted picture.

The prediction picture generation section generates the predictedpicture through a change of either one of a number and a size of theplurality of memories in response to a change in the moving picture ateach time instance.

The prediction picture generation section generates the predictedpicture in a limited use of memories for prediction in response to achange in the moving picture at each time instance.

The prediction picture generation section generates the predictedpicture by calculating a plurality of the predicted pictures generatedby using the respective picture data stored in the plurality ofmemories.

The moving picture prediction system further includes a significancedetector for detecting a feature parameter representing a significanceof the picture segment to be predicted, wherein the prediction picturegeneration section generates the predicted picture by selecting at leastone of choices of at least one of a plurality of prediction methods, theplurality of memories, and a plurality of memory update methods.

The moving picture prediction system further includes a significancedetector for detecting a parameter representing at least one of anamount of bits available for coding the picture segment to be predicted,an amount of change of the picture segment at each time instance, and asignificance of the picture segment, wherein the prediction picturegeneration section generates the predicted picture by selecting at leastone of choices of at least one of a plurality of prediction methods, theplurality of memories, a plurality of memory update methods.

The moving picture prediction system predicts the moving picture on avideo object basis, wherein the moving picture prediction system furtherincludes a significance detector for detecting a parameter representingat least one of an amount of bits available for coding a video object tobe predicted, an amount of change in the video object at each timeinstance, and a significance of the video object, wherein the predictionpicture generation section generates the predicted picture by selectingat least one of choices of at least one of a plurality of predictionmethods, the plurality of memories, and a plurality of memory updatemethods.

The moving picture prediction system further includes a predictioninformation encoder for encoding prediction relating information of themoving picture, wherein the prediction picture generation section countstimes of a memory used for prediction and determines a rank of theplurality of memories based upon a counted number of the times, whereinthe prediction information encoder allocates a code length to theprediction relating information to be encoded based upon the rank of amemory used for prediction.

The plurality of memories includes at least a frame memory for storingthe picture data on a frame basis and a sprite memory for storing asprite picture.

The sprite memory includes at least one of a dynamic sprite memoryinvolving a regular updating, and a static sprite memory not involvingthe regular updating.

The one of the transform methods corresponding to the one of theplurality of memories is at least one of a parallel translation, anaffine transformation, and a perspective transformation in aninterchangeable manner.

Still further, according to the present invention, a method forpredicting a moving picture to be implemented in at least one of anencoding or a decoding, includes the steps of storing picture data forreference to be used for prediction in a plurality of memories,corresponding different transform methods with the plurality ofmemories, respectively, receiving a parameter representing a motion of apicture segment to be predicted, and generating a predicted pictureusing the picture data stored in one of the plurality of memories usedfor predicting the picture segment based upon the parameter and one ofthe transform methods being corresponding to the one of the plurality ofmemories.

The method for predicting a moving picture further includes the steps ofgenerating a prediction memory indication information signal indicatingthe one of the plurality of memories used for the picture segment to bepredicted, and transmitting the prediction memory indication informationsignal and the parameter to a decoding station.

The method for predicting a moving picture is implemented in thedecoding, and further includes the step of receiving a prediction memoryindication information signal indicating the one of the plurality ofmemories used for generating the predicted picture and the parameterrepresenting a motion of the picture segment to be predicted from anencoding station.

Still further, according to the present invention, a method, forpredicting a moving picture to be implemented in at least one of anencoding and a decoding, includes the steps of storing picture data forreference to be used for prediction in a plurality of memories,assigning separate parameter effective value ranges to the plurality ofmemories, respectively, receiving a parameter representing a motion of apicture segment to be predicted, selecting one of the plurality ofmemories assigned to one of the parameter effective value rangesincluding a value of the parameter, and generating a predicted pictureusing the picture data stored in a selected memory.

Still further, according to the present invention, a method, forpredicting a moving picture to be implemented in at least one of anencoding and a decoding, includes the steps of storing picture data forreference to be used for prediction in a plurality of memories,receiving a parameter representing a motion of a picture segment to bepredicted, generating a predicted picture using the picture data storedin the plurality of memories based upon the parameter, and updating thepicture data stored in at least one of the plurality of memories at anarbitrary timing.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a structural diagram of a moving picture encoder according toan embodiment of this invention.

FIG. 2 is a flowchart illustrating an operation of the moving pictureencoder according to the embodiment of this invention.

FIG. 3 is a structural diagram illustrating the configuration of amotion compensator of the moving picture encoder of the embodiment ofthis invention.

FIG. 4 is a flowchart illustrating an operation of the motioncompensator.

FIG. 5 is a structural diagram illustrating the structure of a memoryupdate unit of the moving picture encoder of the embodiment of thisinvention.

FIG. 6 is a flowchart illustrating an operation of the memory updateunit.

FIG. 7 is a structural diagram illustrating the configuration of amotion compensator of a moving picture encoder according to anotherembodiment of this invention.

FIG. 8 is a flowchart illustrating an operation of the motioncompensator of FIG. 7.

FIG. 9 is a structural diagram illustrating the configuration of amotion compensator of a moving picture encoder according to anotherembodiment of this invention.

FIG. 10 is a flowchart illustrating an operation of the motioncompensator of FIG. 9.

FIG. 11 is a structural diagram of a moving picture encoder according toanother embodiment of this invention.

FIG. 12 is a structural diagram showing the configuration of a motioncompensator of the moving picture encoder according to the embodiment ofthis invention.

FIG. 13 is a flowchart illustrating an operation of the motioncompensator of FIG. 12;

FIG. 14 is a structural diagram illustrating the configuration of amemory update unit of a moving picture encoder according to anotherembodiment of this invention.

FIG. 15 is a flowchart illustrating an operation of the memory updateunit of FIG. 14.

FIG. 16 is a structural diagram of a moving picture encoder according toanother embodiment of this invention.

FIG. 17 is a structural diagram of a moving picture encoder according toanother embodiment of this invention.

FIG. 18 is a structural diagram of a moving picture encoder according toanother embodiment of this invention.

FIG. 19 is a structural diagram of a moving picture encoder according toanother embodiment of this invention.

FIG. 20 is a diagram showing bit stream 21 according to the firstembodiment of this invention.

FIG. 21 is a diagram showing bit stream 21 according to the secondembodiment of this invention.

FIG. 22 is a diagram showing bit stream 21 according to the thirdembodiment of this invention.

FIG. 23 is a diagram showing bit stream 21 according to the sixthembodiment of this invention.

FIG. 24 is a structural diagram of a moving picture decoder according toanother embodiment of this invention.

FIG. 25 is a structural diagram illustrating the configuration of amotion compensator of the moving picture decoder according to theembodiment of this invention.

FIG. 26 is a flowchart illustrating an operation of the motioncompensator.

FIG. 27 is an exemplary diagram of interpolation.

FIG. 28 is a flowchart illustrating an operation of a memory update unitof the moving picture decoder according to the embodiment of thisinvention.

FIG. 29 is an exemplary diagram of a video data configuration accordingto the VM encoding system.

FIG. 30 is an exemplary diagram of a VOP data structure.

FIG. 31 is a structural diagram illustrating the configuration of a VMencoder.

FIG. 32 is a flowchart illustrating an operation of the encoder of FIG.31.

FIG. 33 is an exemplary diagram of VOP encoded types and correspondingprediction types.

FIG. 34 is a structural diagram illustrating the configuration of amotion compensator of the encoder of FIG. 31.

FIG. 35 is a flowchart illustrating an operation of the motioncompensator of FIG. 34.

FIG. 36 is a structural diagram illustrating the configuration of amemory update unit of the encoder of FIG. 31.

FIG. 37 is a flowchart illustrating an operation of the memory updateunit of FIG. 36.

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1

FIG. 1 is a block diagram showing the configuration of an encoderaccording to a first embodiment and the following embodiments. Thediagram illustrates an input moving picture signal 1, texture data 2, amotion detector 3, a motion parameter 4, a motion compensator 5, apredicted picture candidate 6, a prediction mode selector 7, aprediction mode 8, a predicted picture 9, a prediction error picture 10,a texture encoder 11, a quantized DCT coefficient 12, a locally decodedprediction error picture 13, a locally decoded picture 14, a memoryupdate unit 15, a memory-a 16, a memory-b 17, a memory-c 18, avariable-length encoder/multiplexer 19, a transmission buffer 20, abitstream 21, a scene-change detector 80, and a timer 81. Particularly,the motion compensator 5 and the memory update unit 15 forms a predictedpicture generation section 100 which implemented a prediction system.Memories a, b, c forms a memory area 200. In the figure, portions notmentioned in this embodiment will be discussed in the followingembodiments. FIG. 2 shows a flowchart illustrating an operating flow ofthe encoder.

This embodiment is based upon the assumption that a plural number, e.g.three, of memories, are used adaptively according to the significance ofan input moving picture based upon such characteristics of motion as anamount of motion and an intensity of color. It is also assumed that thecontent of an arbitrary memory (area), the memory-a for example, areupdated at an arbitrary period of time and a moving picture sequence isreceived on a frame basis.

(1) Input Signal

As aforementioned, the encoder inputs a frame representing a picture ateach time instance of the moving picture sequence and decomposes theframe into the encoding units of macroblocks which are one example ofpicture segments subject to prediction (step S1).

(2) Adaptive Use of Memories

The memories store previously decoded pictures or previously providedfixed pictures. In this embodiment, the three memories are usedadaptively according to the significance of a picture segment in a frameas follows.

The memory-a stores a least significant picture segment (i.e., abackground-like picture segment whose motion is static or flat and thetexture is flat.)

The memory-b stores a less significant picture segment (i.e., a picturesegment of an object whose motion is relatively small.)

The memory-c stores a most significant picture segment (i.e., a picturesegment of an object whose motion is complicated or drastic.)

The least significant picture segment to be stored in the memory-a maybe a background picture segment in a video conference scene or the like.The least significant picture segment also corresponds to a backgroundsegment in a camera-work relating flat motion scene of a full screenincluding slightly moving objects.

With this type of motion, it is efficient to obtain a frame based amountof a motion to substitute for a macroblock based motion, rather than toobtain a macroblock based amount of a motion. Specifically, a transformparameter corresponding to the sprite warping parameter discussed in theconventional art is obtained and the transform parameter of a full frameis then used as the motion parameter of a macroblock in the frame. Themotion parameter may be selected from among a simple paralleltranslation parameter (=a motion vector), an affine motion parameterinvolving transformation, and a perspective motion parameter involvingtransformation. Here, a motion vector is one example of the motionparameter.

The less significant picture segment to be stored in the memory-b may bea picture segment of a moving figure who is not a speaker in a videoconference scene or the like. This segment type of the object may beconsidered less attracting in the scene. The most significant picturesegment to be stored in the memory-c may be a segment of an objectattracting most attention in the video conference scene such as aspeaker.

A picture segment stored in the memory-b or the memory-c representing aunique type of motion of an object should have a macroblock based uniquemotion parameter. The motion parameter of this case may be selected fromamong the simple parallel translation parameter (=a motion vector), theaffine motion parameter involving transformation, the perspective motionparameter involving transformation, etc.

(3) Motion Detection (Step S2)

The motion detector 3 of this embodiment is designed to detect anarbitrary transform parameter of the respective three memories on amacroblock basis, involving no distinction between a motion vector and awarping parameter in the conventional art. The motion detector 3 isprovided with additional functions of a global-motion parameterdetection for detecting a frame based transform parameter using thememory-a and a local-motion parameter detection for detecting amacroblock based transform parameter using the memories a through c.

(4) Motion Compensation (Step S3)

FIG. 3 shows the configuration of the motion compensator 5 of thisembodiment in detail. In the figure, a prediction picture memory addresscalculator 22, a prediction picture memory address 23, a memory reader24, and a reference memory indicator signal 25 which is suppliedexternally are shown. In this embodiment, the reference memory indicatorsignal 25 indicates the use of the memory a, b, c. FIG. 4 shows aflowchart including steps S11 through S16 illustrating an operation ofthe motion compensator 5.

Initially, with an I(Intra)-frame, no motion compensation is performed(step S11). With a frame other than the I-frame, predicted picturecandidates are generated based upon the global-motion and local-motionparameters corresponding to the respective memories detected in themotion detector 3 (steps S12 through S15). Specifically, the predictionpicture memory address calculator 22 calculates the prediction picturememory address 23 of a predicted picture candidate in a memoryidentified by the reference memory indicator signal 25 based upon themotion parameter 4. Upon reception of the prediction picture memoryaddress 23, the memory reader 24 reads out the predicted picturecandidate 6 from a corresponding memory to be outputted.

In this embodiment, the global-motion and local-motion parameters areobtained through the same transform method, thereby allowing the motioncompensator 5 of FIG. 3 to be shared by both global-motion andlocal-motion parameter based approaches of generating a predictedpicture. When generating the predicted picture candidate 6 through theglobal-motion parameter, the memory-a is always used as a referencememory (step S15).

(5) Prediction Mode Selection (Step S4)

The prediction mode of this embodiment is assumed to include thefollowing.

-   (a) a mode for using the memory-a,-   (b) a mode for using the memory-b,-   (c) a mode for using the memory-c, and-   (d) a mode for using an intra-frame coding signal.    Similarly to the discussion in the conventional art, the prediction    mode selector 7 selects the predicted picture candidate 6 having the    least power (amplitude) of a prediction error signal, for example,    from among all the predicted picture candidates 6 generated in the    motion compensator 5 along with an intra-frame coding signal, and    outputs a selected one of the predicted picture candidates 6 as the    predicted picture 9 and an corresponding one of the prediction mode    8. The prediction mode 8 includes memory selection information    indicating a memory used for predicting the selected predicted    picture 9. The prediction mode 8 is transferred to the    variable-length encoder/multiplexer 19 to be encoded with an    allocated length of code in the bitstream 21 as prediction memory    indication information 800.    (6) Memory Updating

The memory update unit 15 controls the memories to be updated. FIG. 5shows the configuration of the memory update unit 15 of this embodimentin detail. In the figure, an activity 26 used for updating the memory-a(which will be discussed later), a memory-a update judger 27, areference memory selector 28, switches 29, 30, picture data 31 forupdating the memory-a, picture data 32 for updating the memory-b,picture data 33 for updating the memory-c, and global prediction picturedata 34 for updating the memory-a are shown. FIG. 6 shows a flow of amemory updating operation.

The memory updating operation of this embodiment has the followingprocedure. Upon reception of the locally decoded picture 14, the memoryupdate unit 15 judges the necessity of updating the memory-a with aframe including the locally decoded picture 14 in the memory-a updatejudger 27 (step S17). The reference memory selector 28 selects a memoryused for predicting the locally decoded picture based upon theprediction mode 8 (steps S18, S19). Then, a reference picture stored ina selected memory is updated with one of the picture data 31, 32, 33 forupdating the memory-a, the memory-b, the memory-c, respectively, and theglobal prediction picture data 34 for updating the memory-a of thelocally decoded picture 14 based upon the following rule. A memory isassumed to be updated each frame on a prediction unit (macroblock)basis.

(1) Frame Based Regular Updating of the Memory-b and the Memory-c (StepsS20, S21):

The locally decoded picture 14 is written into either the memory-b orthe memory-c used for predicting the picture.

(2) Frame Based Adaptive Updating of the Memory-a (Steps S22, S23):

The locally decoded picture 14 is written into the memory-a used forpredicting the picture for an arbitrary frame only or at an arbitraryperiod of time based upon a memory-a update judgement 1000 obtained instep S17.

The content of memory-a is the past record of a time-unvarying picturesegment such as a background picture. This removes the necessity of theregular updating of the content of memory unless a full-screen involvedcomplicated or drastic movement such as a scene change occurs to cause adrastic change in the content of a picture segment.

As aforementioned, a frame based regular updating is performed with acomplicated or drastic area of an object, whereas a longer-term basedupdating is performed with the content of the memory-a, therebyachieving an effective prediction with a background picture half visibleamong moving objects.

Viewed in this light, the memory-a is updated in an arbitrary period oftime in this embodiment. Specifically, possible arbitrary updatecriteria are as follows.

-   a. A full-screen content is updated all at once with a global-motion    parameter indicating a complicated or drastic motion, whereas no    updating operation is performed with the parameter indicating a    rather static motion.-   b. A full-screen content is updated all at once on a predetermined    period basis, regardless of a frame based period of time.-   c. A full-screen content is updated all at once only with a frame    immediately after a scene change detected.

In this embodiment, data as the arbitrary update criteria aregenerically called as the activity 26 used for updating memory-a.Initially, the memory-a update judger 27 judges whether to update thecontent of memory-a based upon the activity 26 (step S17). Specifically,the activity 26 corresponds to a value of the global-motion parameterdetected in the motion detector 3 with the arbitrary update criterion-a,a time stamp of the current frame from the timer 81 with the arbitraryupdate criterion-b, and a flag indicating a scene change detectionoutputted from the scene-change detector 80 with the arbitrary updatecriterion-c.

When the content of memory-a is judged to be updated, the content of thelocally decoded picture 14 is outputted as the global prediction picturedata 34 for updating the content of the memory-a (step S23). When noupdating is judged with the content of the memory-a, then no updating isperformed with the memory-a.

The memory-a update judgement 1000 of a frame is multiplexed in thebitstream 21 to be transmitted to a decoding station so that the sameupdating of the memory-a can be performed with the frame in the decodingstation.

FIG. 20 is a diagram illustrating the bitstream 21 of this embodiment.

FIG. 20 is a conceptual diagram showing how frame data are encoded insequence to be transmitted. Each frame data is provided with headerinformation at the front as a frame based additional information. Theheader information has the memory-a update judgement 1000 multiplexed tobe transmitted to a decoding station. The header information is followedby the component macroblock data of the frame. The macroblock datainclude the prediction memory indication information 800 indicating amemory used for predicting the macroblock data. In a counterpartdecoder, a memory for predicting a predicted picture is specified basedupon the prediction memory indication information 800 of macroblock datato generate the predicted picture.

Although not shown in the figures, the memory-b update informationor/and the memory-c update information may be transmitted to thedecoding station along with, or alternatively to, the memory-a updatejudgement 1000.

The aforementioned encoder thus provides the adaptive and efficient useof two or more memories in response to the content of a moving picturesequence, thereby enhancing prediction efficiency. Specifically, amoving picture sequence is predicted based upon an arbitrary transformparameter through an adaptive use of two or more memories in response tothe content and characteristic of a moving picture sequence. Thisenables an efficient prediction of a moving picture in response to alocal characteristic of a picture by even covering complicated motion.With the enhanced prediction efficiency, the encoder is allowed toreduce an amount of encoded data without deteriorating encoded picturequality. The same prediction system may be employed by the counterpartdecoder for decoding a bitstream encoded through the prediction systemof this invention.

This embodiment has thus disclosed the encoder performing on a framebasis. The same effect may be expected with an alternative encoderperforming on an arbitrary shaped video object (VOP) basis.

Further, this embodiment has thus disclosed the encoder performing on amacroblock basis as the macroblock being a picture segment subjected toprediction. The same effect can be expected with an alternative encoderfor encoding a picture on such a picture segment basis as an arbitraryshaped picture segment and a variable shaped block including fixed-sizeblock components.

Further, this embodiment has thus disclosed the global-motion parameterdetection using the memory-a. Alternatively, a single use of thelocal-motion parameter detection is of course applicable involving noglobal-motion parameter detection. With no global-motion detection, nonecessity occurs for transmitting prediction information indicating aglobal/local prediction as the prediction mode.

Further, this embodiment may include a special memory for predictionwhich stores reference picture data previously generated based upon thecontent of the moving picture sequence. The special memory is notupdated during an encoding operation.

Further, this embodiment has thus disclosed the case that memories a, b,c store a picture segment each time and the memory update unit 15updates one of the memories a, b, c each time. If two or all of thememories a, b, c share to store a picture in part or fully, then thememory update unit 15 updates the two or all of the memories a, b, c. Inthe case of the memory-a being a frame memory for storing a frame ofreference picture data, the memory-b being a static sprite memoryinvolving the adaptive updating, and the memory-c being a dynamic spritememory involving the regular updating, the memory update unit 15 doesnot update the memory-b as the static sprite memory for storingpreviously fixed reference picture data but updates the memory-a and thememory-c concurrently when the memories store the same reference picturesegment. Thus, if a duplicated storage of the reference picture dataoccurs with the memories a, b, c, then the memory update unit 15 updatesa duplicated segment stored in each memory.

The aforementioned can also be applied to the following embodiments.

Further, this embodiment has thus disclosed the use of three memories a,b, c, but alternatively, two of the memories may be utilized.

Further, a counterpart decoder may be provided with the predictionpicture generation section 100 including the same components as themotion compensator 5 and the memory update unit 15 discussed in thisembodiment. A motion compensator provided in the decoder, having nonecessity of generating all the three predicted picture candidates,generates a single predicted picture alone based upon a decoded motionparameter.

Embodiment 2

A second embodiment shows an encoder with a single replacement of themotion compensator 5 of the encoder shown in FIG. 1. The configurationand operation of a motion compensator 5 a of the second embodiment arenow described.

FIG. 7 shows the configuration of the motion compensator 5 a of thisembodiment in detail. The figure includes a reference memory determiner35. FIG. 8 shows a flowchart illustrating a detailed operation of themotion compensator 5 a.

Initially, with the I-frame, no compensation is performed (step S24).With a frame other than the I-frame, the reference memory determiner 35determines a reference memory based upon a value of the motion parameter4 (step S25). The reference memory determiner 35 holds effective motionparameter value ranges (which will be discussed later in detail)allocated, respectively, to the memories a, b, c. The reference memorydeterminer 35 compares the respective effective motion parameter valueranges with the value of the motion parameter 4 to judge which memory isdesignated by the motion parameter 4 and outputs a reference memoryindicator signal 25 a for identifying the respective memories a, b, c.

The effective motion parameter value ranges are effective search rangesallocated to the respective memories for detecting a motion vector, forexample. Specifically, if ±15 pixels are assumed to be given for a totalsearch value range, then the memory-a is chosen to be used forprediction in a range of ±0 to 3 pixels, the memory-b is used in a rangeof ±4 to 8 pixels, and the memory-c is used in a range of ±9 to 15pixels, for example. Here, the reference memory determiner 35 operatesonly when the local-motion parameter is used for prediction, because thememory-a is exclusively used as a reference memory when the predictedpicture candidate is generated based upon the global-motion parameter.This motion-vector value based approach of identifying a memory to beused for prediction is based upon the assumption that a backgroundpicture should include a static motion and a most attractive pictureshould include a complicated or drastic motion. This motion-vector valuebased approach of identifying a memory for prediction involves nonecessity of encoding the prediction mode to be transmitted.

Next, the predicted picture candidate 6 is generated based upon thereference memory indicator signal 25 a of a selected memory (steps S26through S30). Specifically, the prediction picture memory addresscalculator 22 calculates the prediction picture memory address 23 of thepredicted picture candidate 6 in an identified memory by the referencememory indicator signal 25 a based upon the motion parameter 4. Basedupon the prediction picture memory address 23, the memory reader 24reads out the predicted picture candidate 6 from the memory to beoutputted.

As the global-motion and local-motion parameters of this embodiment arebased upon the same transform method, both parameter based approachescan share the motion compensator 5 a of FIG. 7 for generating thepredicted picture candidate. When reading out the predicted picturecandidate 6 based upon the global-motion parameter (step S31), thememory-a is always used as a reference memory.

The effective motion parameter value ranges may be fixed on a movingpicture sequence basis, and alternatively, changed on a frame basis, forexample. With the frame based changes, the effective motion parametervalue ranges assigned to the respective memories of the frame aremultiplexed in a bitstream to be transmitted to a decoding station toperform the same memory selection.

FIG. 21 is a diagram showing the bitstream 21 of this embodiment.

The bitstream is provided with header information added at the front ona moving picture sequence basis. The header information includeseffective motion parameter value range indication information of therespective memories. By thus designating the effective motion parametervalue range indication information at the front of a moving picturesequence, the moving picture sequence is predicted with the fixedeffective motion parameter value ranges in a counterpart decoder.

When varying the effective motion parameter value ranges each frame, theeffective motion parameter indication information is to be included inthe header information added on a frame basis.

Thus, the efficient and adaptive use of the memories in response to themagnitude of a local motion of a frame can be provided by the encoderincluding the motion compensator 5 a, thereby enhancing predictionefficiency.

This embodiment has thus disclosed the encoder performing on a framebasis. The same effect may be expected with an alternative encoderperforming on an arbitrary shaped video object (VOP) basis.

Further, this embodiment has thus disclosed the encoder performing on amacroblock basis. The same effect may be expected with an alternativeencoder for encoding a picture on such a picture segment basis as anarbitrary shaped picture segment and a variable shaped block includingfixed-size block components.

Further, this embodiment has thus disclosed the global-motion parameterdetection using the memory-a. Alternatively, a single use of thelocal-motion parameter detection is of course applicable involving noglobal-motion parameter detection. No global-motion detection involvesno necessity for transmitting information indicating a global/localprediction as the prediction mode.

Further, a counterpart decoder may be provided with the predictionpicture generation section 100 including the same component as themotion compensator 5 discussed in this embodiment. In the decoder, amotion compensator only generates a single predicted picture based upona decoded motion parameter.

Embodiment 3

Another embodiment shows an encoder having a single replacement of themotion compensator 5 of the encoder of FIG. 1. The configuration andoperation of a motion compensator 5 b are now described. A motiondetector 3 a employed in this embodiment is assumed to output an amountof the parallel translation, the affine parameter, and the perspectiveparameter as motion parameters 4 a.

Further, the memory-a of this embodiment is assumed to be a frame memoryfor storing a reference picture frame, the memory-b is assumed to be astatic sprite memory, and the memory-c is assumed to be a dynamic spritememory.

FIG. 9 shows the configuration of the motion compensator 5 b of thisembodiment in detail. In the figure, a parallel translation amount 36(i.e., a motion vector), an affine parameter 37, a perspective parameter38, a parallel-translation based prediction picture memory addresscalculator 39, an affine parameter based prediction picture memoryaddress calculator 40, and a perspective parameter based predictionpicture memory address calculator 41 are shown. FIG. 10 is a flowchartillustrating the operation of the motion compensator 5 b in detail.

Initially, with the I-frame, no prediction is performed (step S33). Witha frame other than the I-frame, the prediction picture memory addresscalculators 39 through 41 calculate the respective prediction picturememory addresses 23 based upon the respective values of the motionparameters 4 a (step S34).

The memory address calculators 39, 40, 41 calculate addresses based uponpicture transform methods assigned, respectively, to the correspondingmemories. In this embodiment, the parallel translation is assigned tothe memory-a, the affine parameter involving such a simpletransformation as a rotation and an expansion/contraction is assigned tothe memory-b, and the perspective parameter involving athree-dimensional complicated motion is assigned to the memory-c. Thesetransform methods may be expressed by the following transformexpressions.

[Parallel Translation]

Amount of parallel translation (a, b):x′=x+ay′=y+b[Affine Transform]

Affine parameter (a,b,c,θ):x′=a(cos θ)x+a(sin θ)y+by′=a(−sin θ)x+a(cos θ)y+c[Perspective Transform]

Perspective parameter (a,b,c,d,e,f):x′=(ax+by+c)/(gx+hy+1)y′=(dx+ey+f)/(gx+hy+1)

Here, (x, y) in a two-dimensional coordinate system represents a pixellocation of an original macroblock. (x′, y′) represents a pixel locationin a memory corresponding to (x, y,) based upon each of the parameters.That is a location in a memory (x′, y′) is calculated based upon theseparameters. Through this mechanism, a memory most suitable for thecharacteristic of a motion can be chosen to be used for prediction on amacroblock basis. With calculated prediction picture memory addresses 23based upon the respective motion parameters 36, 37, 38, the memoryreader 24 reads out the predicted picture candidates 6 fromcorresponding memories to be outputted (steps S35 through S39).

The transform methods assigned to the respective memories of the frameare multiplexed in the bitstream 21 to be transmitted to a decodingstation as a motion detection method indication information so that thesame motion compensation can be performed in the decoding station.

FIG. 22 is a diagram showing the bitstream 21 of this embodiment.

Header information added at the front of a moving picture sequenceincludes the motion detection method indication information. In theencoder, the transformation types to be used in the respective memoriesare interchangeable, and thus the motion detection method indicationinformation indicating a memory-transform method relation is to betransmitted to the counterpart decoder as the header information of themoving picture sequence. Thus, transformation types assigned to be usedwith the respective memories can be identified in the decoder.

In the decoder, the identified transformation types are dynamicallyassigned to the respective memories.

Thus, the efficient and adaptive use of the memories in response to thecharacteristic of a local motion of a frame is provided by the encoderincluding the motion compensator 5 b, thereby enhancing predictionefficiency.

This embodiment has thus disclosed the encoder performing on a framebasis. The same effect may be expected with an alternative encoderperforming on an arbitrary shaped video object (VOP) basis.

Further, this embodiment has thus disclosed the encoder performing on amacroblock basis. The same effect may be expected with an alternativeencoder for encoding a picture on such a picture segment basis as anarbitrary shaped picture segment and a variable shaped block includingfixed-size block components.

Further, this embodiment has thus disclosed the global-motion parameterdetection using the memory-a. Alternatively, a single use of thelocal-motion parameter detection is of course applicable involving noglobal-motion parameter detection. No global-motion detection involvesno necessity of transmitting information of a global/local prediction asthe prediction mode.

Further, this embodiment has thus disclosed the use of the memories a,b, and c. Alternatively, the use of memories a and b alone, memories aand c alone, or memories b and c alone, is also applicable.

Further, a decoder may be provided with the prediction picturegenerating section 100 including the same component as the motioncompensator 5 b discussed in this embodiment. A motion compensator in adecoder only generates a single predicted picture based upon a decodedmotion parameter.

Embodiment 4

Another embodiment shows an encoder which receives a plural number, twofor example, of different video objects, having shape information,intermingled in a moving picture sequence for a collective encoding.FIG. 11 shows the configuration of the encoder of this embodiment.

In the figure, an input picture frame 42, an object separator 43, objectdata 44 a, 44 b, shape blocks 45 a, 45 b, switches 46 a, 46 b, shapeencoders 47 a, 47 b, compressed shape block data 48 a, 48 b, locallydecoded shape blocks 49 a, 49 b, texture data (macroblocks) 50 a,50 b,motion detectors 51 a, 51 b, motion parameters 52 a, 52 b, motioncompensators 53 a, 53 b, predicted picture candidates 54 a, 54 b,prediction mode selectors 55 a, 55 b, prediction mode information 56 a,56 b, predicted pictures 57 a, 57 b, prediction error signals 58 a, 58b, texture encoders 59 a, 59 b, compressed texture data 60 a, 60 b,locally decoded prediction error signals 61 a, 61 b, locally decodedmacroblocks 62 a, 62 b, a memory update unit 63, memory-a 64, memory-b65, memory-c 66, memory-d 67, memory-e 68, memory-f 69, variable-lengthencoders 70 a, 70 b, a multiplexer 71, a buffer 72, a bitstream 73, amemory section 94, an object-A encoder 88 a for encoding an object-A,and an object-B encoder 88 b for encoding an object-B are shown. Theobject encoders 88 a, 88 b are structurally identical to each other withthe identical components.

This encoder inputs the picture frame 42, which is decomposed into theencoding units of objects in the object separator 43. The objectseparator 43 is assumed to be assigned a processing method arbitrarily.

The shape information of an object is transferred to the shape encoder47 a, 47 b in a form of the shape block 45 a, 45 b to be encoded, andthen transferred to the variable-length encoder 70 a, 70 b as thecompressed shape block data 48 a, 48 b.

The motion detector 51 a, 51 b detects a motion parameter based upon thelocally decoded shape block 49 a, 49 b in the same manner as that of theVM encoding system. A motion parameter can be detected on a macroblockbasis by using all the memories a through f.

As a rule, however, the memories a through c are designed to be used foran object-A to be encoded in the object-A encoder 88 a, and the memoriesd through f are designed to be used for an object-B to be encoded in theobject-B encoder 88 b.

Also, as for a motion type, an arbitrary transform parameter is assumedto be detected on a macroblock basis with all the memories in the memorysection 94, involving no distinction between the motion vector and thewarping parameter.

The motion compensator 53 a, 53 b generates all the predicted picturecandidates 54 a, 54 b based upon the respective motion parameters 52 a,52 b. Then, in the prediction mode selector 55 a, 55 b, the predictedpicture 57 a, 57 b is obtained along with the prediction modeinformation 56 a, 56 b. The predicted picture 57 a, 57 b is thendifferentiated from an original signal or the texture data 50 a, 50 b toobtain the prediction error signal 58 a, 58 b, which is encoded in thetexture encoder 59 a, 59 b to be transmitted to the variable-lengthencoder 70 a, 70 b. The locally decoded prediction error signal 61 a, 61b is added to the predicted picture 57 a, 57 b to obtain the locallydecoded macroblock 62 a, 62 b to be stored into the memories a through fin accordance with an indication by the memory update unit.

Object A/B data when encoded in the object-A/B encoder 88 a, 88 b aremultiplexed in the bitstream 73 at the multiplexer 71 to be transmittedvia the buffer 72.

The prediction of this embodiment is discussed below focusing on themotion compensator 53 a, 53 b playing a primary role in the prediction.

The motion compensator 53 a, 53 b of this embodiment generates apredicted picture candidate based upon the motion parameter 52 a, 52 bdetected in the motion detector 51 a, 51 b. FIG. 12 shows theconfiguration of the motion compensator 53 a in detail. FIG. 13 shows aflowchart illustrating the operation of the motion compensator 53 a inthe object-A encoder 88 a.

In FIG. 12, an object-B reference judger 74 a and an object-B referenceindicator flag 75 a are shown.

The motion parameter 52 a includes memory information used fordetection. A predicted picture candidate is generated based upon aparameter value through the prediction picture memory address calculator22 a and a memory reader 24 a in the same manner as that stated in thefirst embodiment (step S44 through step S49). The object-B referencejudger 74 a judges if the memories assigned to object-B are used forpredicting the current macroblock based upon the reference memoryinformation included in the motion parameter 52 a (step S43).

The object-B reference judger 74 a outputs a judged result as theobject-B reference indicator flag 75 a, which is multiplexed in thebitstream 73 to be transmitted to a decoding station so as to be usedfor deciding whether the object can be reproduced in a single use of thememories a, b, c of self in the decoding station. In order to secure thesingle use of the memories of self when reproducing the object in thedecoding station, a limited use of the memories (a, b, c alone) of selffor prediction can be controlled by an externally supplied signal 85 aat the time of encoding the object.

Thus, the efficient and adaptive use of the memories in response to thecharacteristic of a local motion of a frame is provided by the encoderincluding the motion compensator 53 a, 53 b, thereby achieving anefficient prediction.

This embodiment has thus disclosed the encoder for encoding an object ona macroblock basis. The same effect may be expected with an alternativeencoder for encoding a picture on such a picture segment basis as anarbitrary shaped picture segment and a variable shaped block includingfixed-size block components.

Further, a decoder may be provided with the same components as themotion compensator 53 a, 53 b of this embodiment. A motion compensator53 of the decoder only generates a single predicted picture based upon adecoded motion parameter. Further, if the decoder is structured so as toacknowledge whether a decoding object can be reproduced by itself by wayof decoding a bit corresponding to object reference indicator flag 75 a,75 b of the other object in a bitstream, then an error-free securedreproduction of decoded object data can be achieved.

Embodiment 5

Another embodiment shows an encoder where the number of memories or thesize of a memory can be varied flexibly in response to a change in avideo object at each time instance. The encoder of a fifth embodimentmodifies the encoder of FIG. 1 with a replacement of the memory updateunit 15.

FIG. 14 shows the configuration of a memory update unit 15 a of thisembodiment in detail. In the figure, a memory expansion judger 76, amemory expansion indicator signal 77, and a memory contraction judger78, and a memory contraction indicator signal 79 are shown. FIG. 15shows an operating flow (step S51 through S63) of the memory update unit15 a.

A picture substantially different from the past record of a movingpicture sequence stored in the memories may occur due to a scene changeor the like. This may cause a deterioration of prediction efficiencyafter the scene change if reference pictures stored in the existingmemories are the only available. For such an occasion, the scene-changedetector 80 detects a scene change, a frame appearing immediately afterthe detected scene change is subject to intra-frame coding or the like,and resultant intra-frame coded data are stored additionally in a memoryas new reference data, thereby enhancing prediction efficiencythereafter.

Further, in consideration of the physical limitation of storagecapacity, a flexible approach of contracting the portions which arerarely used for prediction of the reference pictures stored in thememories is introduced. Specifically, the frequency in use of memoryareas for prediction of the respective memories a, b, c is examined inthe memory update unit 15 a based upon the prediction mode 8.Consequently, the memory update unit releases a memory area identifiedlow in frequency from an area for use. For example, with a softwarebased implementation of this encoder, limited RAM resources may be usedeffectively.

Viewed in this light, the memory update unit 15 a of this embodiment isprovided with a function of expanding a memory area in response to eachtime instance of a time-varying moving picture sequence and contractinga memory area including a reference picture rarely used for prediction.

The memory-a, similarly to the first embodiment, is judged in thememory-a update judger 27 whether to be updated (step S50). Whenupdating the memory-a, the locally decoded picture 14 is written intothe memory-a (steps S56, S57). The locally decoded picture 14 is writteninto the other memories as well in accordance with the prediction mode 8(step S51 through S55).

The updating of the contents of the memories involves the judgement ofmemory expansion/contraction. The memory expansion judger 76 judgeswhether to expand the size of the memory-a (or the memory-b, or thememory-c) based upon the activity 26 used for updating the memory-a(steps S58 through S60). When a positive judgement is made due to ascene change or the like, the expansion of the memory is indicated bythe memory expansion indicator signal 77. The memory contraction judger78 counts the times of a memory area used for prediction based upon theprediction mode 8. With a memory area counted less than a predeterminednumber in use for prediction, the contraction of the memory area isindicated by the memory contraction indicator signal 79 (steps S61through S63).

Thus, a highly efficient prediction can be achieved in response to eachtime instance of a time-varying moving picture sequence by the encoderincluding the memory update unit 15 a. In addition, the dynamicallocation of memory areas required for prediction contributes to theenhancement of prediction efficiency and the effective use of memoryresources.

This embodiment has thus disclosed the encoder performing on a framebasis. The same effect may be expected with an alternative encoderperforming on an arbitrary shaped video object (VOP) basis.

Further, this embodiment has thus disclosed the encoder for encoding aframe on a macroblock basis. The same effect can be expected with analternative encoder for encoding a picture on such a picture segmentbasis as an arbitrary shaped picture segment and a variable shaped blockincluding fixed-size block components.

Further, a counterpart decoder may be provided with the same componentas the memory update unit 15 a discussed in this embodiment.

Embodiment 6

With reference to the respective previous embodiments, the memories tobe used for prediction are changed on a macroblock basis. Alternatively,the memories to be used for prediction can be changed on a frame or avideo object basis. This eliminates the necessity of encoding memoryrelating information to be encoded on a frame or a video object basisand memory selection information (which is included in the predictionmode 8) to be encoded on a macroblock basis, thereby achieving anefficient encoding.

With reference to the encoder of FIG. 1 of the first embodiment, forexample, the macroblock based changes of the memories used forprediction create the necessity of transmitting additional informationidentifying a memory used for prediction on a macroblock basis.According to this embodiment, the changing unit of the memories to beused for prediction is limited to a frame or a video object, therebyeliminating the additional information to be transmitted on a macroblockbasis effectively. FIG. 23 shows a difference of the transmissionbitstream 21 of this embodiment from the transmission bitstream 21 ofFIG. 20 of the first embodiment. The bitstream of FIG. 23 represents aframe based change of the memories to be used for prediction with theprediction memory indication information 800 included in frame basedheader information. The bitstream of FIG. 23 may be effective, forexample, in the case that the picture characteristic of a moving picturesequence changes infrequently including little changes locally on amacroblock level. Further, a decoder may be provided so as to decode thethus encoded bitstream to reproduce a frame or a video object.

Embodiment 7

With reference to the previous embodiments, two predicted picturecandidates read out from an arbitrary plural number, two (e.g., memoriesa and b) for example, of the memories are subject to an arithmetic meanto obtain a picture as a member of the predicted picture candidates 6 oras the predicted picture 9. Further, a decoder may be provided so as todecode the thus encoded bitstream to reproduce a frame or a videoobject.

Embodiment 8

With reference to the encoders of the previous embodiments, a previouslydetected feature parameter representing the spatial complexity,perceptual significance and the like of a picture segment as aprediction unit may be utilized as tools for deciding a prediction modeand for judging the updating of the memories.

For example, a moving picture is assumed to include a motion toocomplicated to encode data in an acceptable quality within a givenamount of encoding. In this case, significance is examined on aprediction picture segment (e.g., a macroblock, an arbitrary shapedpicture segment, an arbitrary shaped block) basis. Consequently, a lowquality encoding is assigned to some extent to a less significantsegment in order to save some amount of encoding for a more significantsegment, thereby improving an overall picture quality. With the encodersof this invention where two or more memories are switchedinterchangeably at an arbitrary timing to be used for prediction, a moreadaptive prediction can be achieved in response to the characteristic ofa picture, through detecting a feature parameter representing thesignificance of a prediction picture segment and then determining theuse of the memories dynamically based upon a detected feature parameter.For example, as shown in FIG. 16, a segment-significance detector 95 isprovided for detecting the feature parameter on a segment basis todetermine the significance of the segment. The segment-significancedetector 95 transfers a segment-significance to a prediction modeselector 7 a and a quantization parameter based upon thesegment-significance to a texture encoder 11 a. With a segment judgedmore significant in the segment-significance detector 95, a most complexmode among two or more prediction modes available is used forprediction. Specifically, reference pictures from the respectivememories a, b, c are used to obtain the motion parameters and thepredicted pictures, respectively, based upon a complex motion model. Inthe prediction mode selector 7 a, a prediction mode having the highestprediction efficiency is selected from among modes including anarbitrary combination (e.g., an arithmetic mean) of the predictedpictures. At the same time, reference pictures of all the memories usedfor prediction are updated. The texture encoder 11 a performs anencoding using a quantization parameter having a smaller quantizationstep size. With a less significant segment, a simplified prediction mode(i.e., a parallel translation amount detection using a single memory) isemployed for prediction and a quantization parameter having a largerquantization step size is utilized for encoding, regardless of theamplitude of an obtained prediction error signal, so that an amount ofencoding be reduced. Through this control, a less significant segmentreduces its picture quality to some extent and a more significantsegment maintains its quality through a high-quality prediction, therebyimproving an overall quality within a given amount of encoding.

Embodiment 9

In an encoder where a moving picture sequence is predicted and encodedby using two or more memories, a parameter representing an amount ofencoding available for the moving picture sequence at each timeinstance, an amount of a change in a scene at a certain time instance(e.g., a scene change detection), or the feature parameter orsignificance of a prediction picture segment described in the eighthembodiment may be detected previously. The values of these parametersmay be used for predicting a picture at a particular time instance in aprediction system. Alternatively, these values may be utilized asjudging tools for selecting a reference memory area in a predictionsystem. A frame-significance detector 96 may be provided for determiningthe significance on a frame basis as shown in FIG. 17. Theframe-significance detector 96 detects, for example, an amount of achange in a motion between the current and the previous frame (e.g., ascene change detection by the scene change detector 80), the appearanceof a new object or the disappearance of an object or the like. A finalsignificance of the current frame is determined in consideration of anamount of encoding available for the current frame informed by thetransmission buffer 20. Based upon the final significance, a moresignificant frame may be predicted by using all the prediction methodsand reference memory areas available for the maximum possibleimprovement of prediction efficiency, whereas a less significant frameis predicted in a limited use of the prediction methods and thereference memory areas for a simplified encoding so as to reduce thethroughput. An alternative encoder for performing intra-frame codingalone involving no prediction at a scene change may be possible. Inaddition, a more sophisticated quality control may be achieved with ajoint use of the segment-significance detector 95 discussed in theeighth embodiment. Through this control, a less significant framereduces its quality to some extent and a more significant framemaintains its quality by a high-quality prediction, thereby improving anoverall picture quality within a given amount of encoding.

The idea of this embodiment is also applicable to a software basedencoding being associated with unsteady transaction processes andunsteady size of available storage in order to achieve an efficientencoding in the maximum use of available resources. This reduces athroughput with a less significant frame, thereby accelerating a generalprocessing speed.

Embodiment 10

In an encoder where a moving picture sequence including two or morevideo objects is predicted and encoded by using two or more memories, asshown in FIG. 11, a parameter representing a gross amount of encodingavailable for the sequence, an available amount of encoding of a videoobject at each time instance, an amount of a change in a video object ateach particular time instance (e.g., the appearance/disappearance of anobject), a level of significance/attention of a video object in aparticular scene, or the feature parameter or significance of aprediction picture segment discussed in the eighth and ninth embodimentsmay be detected previously. The values of these parameters may beutilized for predicting a video object at each particular time instance.Alternatively, these values may be utilized as judging tools forselecting a reference memory area.

For example, as shown in FIG. 18, significance detectors 97 a through 97n responsive, respectively, to objects 1 through n may be provided fordetecting a parameter representing an amount of a change in an object ateach time instance, or the appearance/disappearance of an object. Inaddition, the significance of an object at each time instance isdetermined in consideration of the occupational proportion of a buffer72 x for storing the encoded data of all the objects and theoccupational proportion of virtual buffers 72 a through 72 n for therespective objects. When a new type of segment appears as a result of anobject having another object overlapped in part, for example, then thefollowing control may be applied to this type of segment because thistype of segment has a great influence on prediction efficiencythereafter. A higher significance may be assigned to this type ofsegment to obtain an encoded picture in high quality even without enoughspace available for storage in the corresponding virtual buffer of theobject. Significance detected in the significance detectors 97 a through97 n is transferred to object 1 through N encoders 98 a through 98 n,where a full use of the prediction methods and the reference memoryareas available is allowed to a more significant object so as to improveprediction efficiency to the maximum, whereas a limited use of theprediction methods and the reference memory areas is assigned to a lesssignificant object so as to simplify the encoding, thereby reducing thethroughput. Further, with an encoder for encoding objects decomposedfrom a frame through a real time separation, when a considerable amountof a change occurs in the contents of the object due to the appearanceof a new object or the disappearance of an existing object, the objectmay be subject to intra-frame coding alone with no prediction involved.A more sophisticated quality control may be achieved on a predictionsegment basis of an object in a joint use of the object 1 through Nencoders 98 a through 98 n and the segment-significance detector 95discussed in the eighth embodiment. Through this control, a lesssignificant object is reduced in quality to some extent and a moresignificant object manages to maintain its quality through asophisticated prediction, thereby improving an overall quality within agiven amount of encoding.

Embodiment 11

An alternative encoder may be provided with a prediction informationencoder 91 for allocating a code (encoding) to prediction relatingencoding information (e.g., a reference memory number) as shown in FIG.19.

In the encoder where a moving picture sequence or a video object ispredicted and encoded by using the memories a, b, c, the memories may beranked based upon frequency in use for prediction with ranks beingupdated dynamically during an encoding operation. Consequently, a codeallocation is performed to the prediction relating encoding information(e.g., a reference memory number) based upon the ranks of the respectivememories used for prediction in the prediction information encoder 91.

For example, in the encoder of FIG. 19, the memory update unit 15 b maybe provided with a counter 92 which counts the times of the respectivememories a, b, c to be used for prediction, ranks the memories a, b, cbased upon counted values, and outputs resultant ranking information 90.This ranking may be performed on a picture (VOP) basis at a particulartime instance of a frame or a video object, and alternatively, on asmaller unit basis of a prediction picture segment (e.g., a macroblock,an arbitrary shaped segment, and an arbitrary shaped block).

This shows how often the respective memories are used for prediction. Amemory in a frequent use for prediction is the most significant forprediction, and thus, a high frequency in use for referencecorresponding to a high rank.

When encoding information on the frequency in use for prediction of thememories on a prediction picture segment basis, a memory in a frequentuse for reference (i.e., a high-rank memory) is allocated a short codeto enhance encoding efficiency.

In addition, if the motion parameter detected on a prediction picturesegment basis is allocated a code length in response to the rank of amemory used for reference, then a shorter code may be assigned to amotion parameter value generated frequently, thereby achieving anefficient encoding of the prediction information. This may bematerialized with an alternative encoder where the predictioninformation encoder 91 in the variable-length encoder/multiplexer 19receives the ranks of the respective memories from the counter 92 in thememory update unit 15 b and encodes the prediction information using avariable-length code based upon the ranking information 90.

Embodiment 12

FIG. 24 shows the configuration of a picture decoder where an encodeddigital picture through compression is reproduced through expansionaccording to another embodiment. In the figure, the encoded bitstream21, a variable-length decoder 119, the quantized DCT coefficient 12, aquantization orthogonal transform coefficient 12 a, a quantization step12 b, a texture decoder 111, a dequantizer 111 a, an inverse orthogonaltransformer 111 b, a decoding adder 190, a decoded picture 101, adisplay controller 191, the prediction mode 8, memory-b updateinformation 1001, memory-c update information 1002, the motion vector 4(a motion parameter), the prediction memory indication information 800,an in-screen location 195 of a prediction picture segment, a motioncompensator 105, a memory-a 116, a memory-b 117, a memory-c 118, amemory update unit 115, and a predicted picture 106 are shown. Themotion compensator 105 and the memory update unit 115 form a predictionpicture generation section 100 a. The memories a, b, c form a memoryarea 200 a.

According to this embodiment, the memory-a is assumed to be a framememory designed to store a frame of picture data, the memory-b isassumed to be a static sprite memory, and the memory-c is assumed to bea dynamic sprite memory. The decoder of this embodiment is assumed toreceive the bitstream 21 of FIG. 22. Although not shown in FIG. 22, thememory-b update information 1001 and the memory-c update information1002 are assumed to be transmitted in the bitstream. The memory-b updateinformation 1001 is assumed to include an update indication for a fullupdating of the static sprite memory and picture data for the fullupdating. Similarly, the memory-c update information 1002 is assumed toinclude an update indication for a full updating of the dynamic spritememory and picture data for the full updating.

The operation of the thus configured decoder is described below. Thevariable-length decoder 119 analyzes the bitstream 21 and decomposes itinto separate encoded data. The quantization orthogonal transformcoefficient 12 a is transferred to the dequantizer 119 a to bedequantized by using the quantization step 12 b. A dequantized result issubject to inverse orthogonal transformation in the inverse orthogonaltransformer 111 b to obtain a decoded texture, which is transferred tothe decoding adder 190. Orthogonal transformation employed here is thesame as that employed in an encoding station such as Discrete CosineTransformation (DCT).

The motion compensator 105 inputs the motion vector 4, the predictionmemory indication information 800, and information indicating thein-screen location 195 of a prediction picture segment included in thebitstream 21, all of which are decoded in the variable-length decoder119. The motion compensator 105 reads out a right predicted picture fromreference pictures stored in the memories a, b, c based upon the threekinds of information. The in-screen location 195 of a prediction picturesegment can be obtained by counting the number of macroblocks, otherthan from the information included in the bitstream. The process ofgenerating a predicted picture will be discussed in a later section fordescribing the operation of the motion compensator 105 in detail.

The decoding adder 190, based upon the information of the predictionmode 8, outputs an output from the inverse orthogonal transformer 111 bdirectly as the decoded picture 101 with a block through intra-framecoding, and, with a block through inter-frame coding, adds an outputfrom the inverse orthogonal transformer 111 b to the predicted picture106 to be outputted as the decoded picture 101. The decoded picture 101is transferred to the display controller 191 to be outputted to adisplay device and also transferred to the memories a, b, c to be storedas a reference picture for a later use in decoding. A memory writingoperation is controlled by the memory update unit 115 based upon theprediction mode 8.

A predicted picture generation performed in the motion compensator 105in the prediction picture generation section 100 a is now discussed.According to this embodiment, the prediction method of a picture isdetermined based upon the prediction memory indication information 800.The decoder of this embodiment generates a predicted picture using areference picture through predetermined coordinate transformation andinterpolation based upon the motion vector 4 and the prediction memoryindication information 800. Coordinate transform methods are assignedpreviously to the respective memories to be used for prediction. Forexample, the following approaches are possible similar to the picturetransform methods described in the third embodiment.

-   (1) the memory-a used for prediction (with the prediction memory    identification information 800 indicating the use of the memory-a)

The coordinates of each pixel of a prediction segment are translatedbased upon the motion vector and picture data at a correspondinglocation in the memory-a is read out as the predicted picture.

-   (2) the memory-b used for prediction (with the prediction memory    identification information 800 indicating the use of the memory-b)

An affine transform expression is found based upon the motion vector,the coordinates of each pixel of a prediction segment are displacedbased upon the transform expression, and picture data at a correspondinglocation in the memory-c is read out as a predicted picture.

-   (3) the memory-c used for prediction (with the prediction memory    identification information 800 indicating the use of the memory-c)

A perspective transform expression is found based upon the motionvector, the coordinates of each pixel of a prediction segment aredisplaced based upon the transform expression, and picture data at acorresponding location in the memory-b is read out as a predictedpicture.

FIG. 25 shows the configuration of the motion compensator 105 in detail.In the figure, a switch 161, a corresponding point determiner 162 forthe memory-a, a corresponding point determiner 163 for the memory-b, acorresponding point determiner 164 for the memory-c, a memory readaddress generator 165, a switch 166, and an interpolator 167 are shown.FIG. 26 is a flowchart illustrating the optation of the motioncompensator 105.

The operation of the motion compensator 105 of this embodiment isdescribed below with reference to FIGS. 25 and 26.

1) Determining a Corresponding Point

Initially, the corresponding point determiner of a corresponding memoryis selected by the switch 161 based upon the prediction memoryindication information 800. The vector 4 is then inputted to a selectedcorresponding point determiner. In this section, a predicted picturelocation corresponding to each memory is calculated, which is explainedbelow with each memory.

1-1) The Memory-a Indicated by the Prediction Memory IndicationInformation 800 (Step S100)

A predicted picture location is calculated through parallel translationbased upon a motion vector (step S101). Specifically, a predictedpicture location (x′,y′) corresponding to a pixel at a predictionpicture segment location (x,y) is determined based upon a motion vector(a, b) according to the following expression.x′=x+ay′=y+bA determined predicted picture location is outputted to the memory readaddress generator 165.1-2) The Memory-b Indicated by the Prediction Memory IndicationInformation 800 (Step S103)

An affine transform expression is determined based upon the motionvector 4. Specifically, an affine parameter (a, b, c, θ) of thefollowing expression is determined by using the motion vector of avertex of a rectangular area enclosing a prediction picture segment,x′=a(cos θ)x+a(sin θ)y+by′=a(−sin θ)x+a(cos θ)y+cthereby obtaining the predicted picture location (x′,y′) correspondingto a pixel at the location (x,y) of a prediction picture segment to beoutputted to the memory read address generator 165 (step S104).1-3) The Memory-c Indicated by the Prediction Memory IndicationInformation 800 (Step S106)

A perspective transform expression is determined based upon a motionvector. Specifically, a perspective parameter (a, b, c, d, e, f) of thefollowing expression is determined by using the motion vector of avertex of a rectangular area enclosing a prediction picture segment,x′=(ax+by+c)/(gx+hy+1)y′=(dx+ey+f)/(gx+hy+1)thereby obtaining the predicted picture location (x′,y′) correspondingto a pixel at the location (x,y) of a prediction picture segment to beoutputted to the memory read address generator (step S107).2) Reading Out Data for Generating a Predicted Picture

Based upon the predicted picture location (x′, y′) outputted from aselected corresponding point determiner, the memory read addressgenerator 165 generates a memory address for specifying the location ofpicture data required for generating a predicted picture in a referencepicture stored in a memory, and reads out the data for generating apredicted picture (steps S102, 105, 108).

3) Generating a Predicted Picture

Among the component pixels of a predicted picture, with a pixel at aninteger pixel location, the data for generating a predicted picture isused directly as a component pixel of a predicted picture, and with apixel at a real number precision pixel location, the data for generatinga predicted picture is subject to interpolation in the interpolator 167to generate an interpolated pixel value (steps S109, S110, S111). FIG.26 illustrates an interpolated pixel value generation. In FIG. 26, (i₀,j_(p)) denotes an integer pixel location, (j^(p), j^(p)) denotes a realnumber precision pixel location, and w denotes a weight.

4) Updating a Memory (a Reference Picture)

FIG. 28 shows a flowchart illustrating a control operation of the memoryupdate unit 115. The memory update unit 115 controls an updating of therespective memories on a readout unit basis (e.g., a macroblock) of apredicted picture based upon the prediction mode 8 (or the predictionmemory indication information 800). With the memory-a used forprediction (step S112), the contents of the memory-a and the memory-care updated regularly with the decoded picture 101 (step S113). With thememory-b used for prediction (step S114), the reference picture of thememory-b is not updated on a readout unit basis of a predicted picturebecause of the memory-b being a static sprite memory, whereas thecontents of the memory-a and the memory-c are updated regularly with thedecoded picture 101 (step S115). When receiving the update indication bythe memory-b update information 1001, then the memory update unitupdates a full content of the memory-b with received picture dataincluded in the memory-b update information 1001 (step S116). With thememory-c used for prediction (step S117), the contents of the memory-aand the memory-c are updated regularly by using the decoded picture 101(step S118). When receiving the update indication by the memory updateinformation, the memory update unit updates the content of the memory-cwith received picture data included in the memory-c update information1002 (step S119).

The use of the three memories a, b, c of this embodiment may be replacedby the use of two memories thereof, for example, with the memories a andb, that is, a frame memory and a static sprite memory. Alternatively,the memories a and c, that is, a frame memory and a dynamic memory, maybe used.

As aforementioned, according to the decoder of this embodiment, thebitstream 21 encoded through an efficient prediction using the variouskinds of motion parameters in response to the motion of a picture can bedecoded. In addition, the decoder is applicable to the arbitraryupdating approach of the contents of a reference picture at a timingdetermined in the encoding station, thereby achieving a more adaptivedecoding in response to the characteristic of a picture.

According to this embodiment, if the bitstream includes a predictionerror signal encoded through encoding other than orthogonal transformencoding, the same effect may be obtained by replacing a component fordecoding a prediction error signal, other than the motion compensatorand memory update unit.

Further, this embodiment may be applied not only to a decoder fordecoding data on a fixed-size block basis, e.g., for decoding a normaltelevision signal on a frame basis, but also to a decoder for decodingan arbitrary shaped video object (e.g., a Video Object Plane disclosedin ISO/IEC JTC1/SC29/WG11/N1902) as a unit without limiting a predictionsegment to a fixed-size block.

INDUSTRIAL FEASIBILITY

As discussed above, the memory areas provided for storing referencepictures according to this embodiment enables the adaptive use of thememories for storing data based upon the characteristic of the movingpicture sequence. In addition, the contents of one or more of the memoryareas can be updated at an arbitrary timing, so that the content of atime-unvarying picture, such as a background picture, is controlled tobe updated on a longer-term basis, and the contents of a locallychanging picture segment is controlled to be updated on a regular orsequential basis. This achieves an efficient prediction by reflectingthe past record of the moving picture sequence.

Further, the transform parameter value ranges are assigned to the memoryareas for making the respective memory areas effective, and the memoryareas are switched to be used for prediction among them based upon thevalue of the transform parameter of a prediction picture segment,thereby achieving an efficient prediction in response to the magnitudeof a local/global motion of the moving picture sequence. At the sametime, the motion parameters to be encoded on a prediction picturesegment basis can be encoded efficiently within the effective motionparameter value ranges of the reference memory areas.

Further, to the respective memory areas, the transform methods becomingeffective in the respective memories are assigned, and the memories areswitched to be used for prediction among them in response to the type ofthe transform parameter of a prediction picture segment, therebyachieving an efficient prediction in response to the complexity of alocal/global motion of the moving picture sequence. At the same time,the transform method can be selected adaptively in response to thecharacteristic of a prediction picture segment, thereby achieving anefficient encoding of the motion parameter.

1. A moving picture prediction system for predicting a moving picture tobe implemented in at least one of an encoder and a decoder, the movingpicture prediction system comprising: a plurality of reference picturememory areas, each area for storing picture data of a reference pictureto be used for prediction; and a prediction picture generation sectionincluding a motion compensator for receiving a parameter representing amotion of between an image to be predicted and a reference picturestored in a reference memory area, a indication information indicating areference picture data to be used for prediction stored in the referencepicture memory area and a updating information indicating a timing ofupdating the reference picture memory, and for generating a predictedimage by using the reference picture data indicated by the indicationinformation, and a memory update unit for controlling the period of timeof each reference picture data stored in the reference picture memoryareas based upon the updating information received.
 2. The movingpicture prediction system according to claim 1, wherein the period oftime is divided into long period and short period, wherein the longperiod is longer than a period of storing each reference period and theshort period is the period of storing.
 3. The moving picture predictionsystem according to claim 1, wherein the period of time comprising atleast long period, the long period is longer than an interval of frames.4. The moving picture prediction system according to claim 1, whereinsome of reference pictures are stored in the reference picture memoryfor more than an interval of frames.
 5. A moving picture predictionmethod of predicting a moving picture to be implemented in at least oneof an encoder and a decoder, the moving picture prediction methodcomprising the steps of: receiving a parameter representing a motion ofbetween an image to be predicted and a reference picture stored in areference memory area, a indication information indicating a referencepicture data to be used for prediction stored in the reference picturememory area and a updating information indicating a timing of updatingthe reference picture memory, each area for storing picture data of areference picture to be used for prediction; generating a predictedimage by using the reference picture data indicated by the indicationinformation; and controlling the period of time of each referencepicture data stored in the reference picture memory areas based upon theupdating information received.
 6. The moving picture prediction methodaccording to claim 5, wherein the period of time is divided into longperiod and short period, wherein the long period is longer than a periodof storing each reference period and the short period is the period ofstoring.
 7. The moving picture prediction method according to claim 5,wherein the period of time comprising at least long period, the longperiod is longer than an interval of frames.
 8. The moving pictureprediction method according to claim 5, wherein some of referencepictures are stored in the reference picture memory for more than aninterval of frames.
 9. A moving picture prediction system for predictinga moving picture to be implemented in at least one of an encoder and adecoder, the moving picture prediction system comprising: a plurality ofreference picture memory areas, each area for storing picture data of areference picture to be used for prediction; and a prediction picturegeneration section including a motion compensator for receiving aparameter representing a motion of between an image to be predicted anda reference picture stored in a reference memory area and a updatinginformation indicating a timing of updating the reference picturememory, and for generating a predicted image by using the referencepicture data stored in the plurality of the reference picture memoryareas; and a memory update unit for controlling the number of referencepicture memory areas to be used for generating a predicted picture,based on the updating information.
 10. The moving picture predictionsystem according to claim 9, wherein the memory update unit furtherupdates the picture data in at least one of the plurality of memoryareas, and controls the number of reference picture memory areas bydecreasing the number of reference picture memory areas by releasing amemory area based on the updating information.
 11. A moving pictureprediction method of predicting a moving picture to be implemented in atleast one of an encoder and a decoder, the moving picture predictionmethod comprising the steps of: receiving a parameter representing amotion of between an image to be predicted and a reference picturestored in a reference memory area and a updating information indicatinga timing of updating the reference picture memory; generating apredicted image by using a reference picture data stored in a pluralityof reference picture memory areas, each area for storing picture data ofthe reference picture to be used for prediction; and controlling thenumber of reference picture memory areas to be used for generating apredicted picture, based on the updating information.
 12. The movingpicture prediction method according to claim 11, further comprising thestep of: updating the picture data in at least one of the plurality ofmemory areas, wherein the step of controlling the number of referencepicture memory areas by decreasing the number of reference picturememory areas by releasing a memory area based on the updatinginformation.